International Journal of Digital Earth, Volume 3, Issue 1 March 2010 , pages 47 – 71

William J. Morphet; Jürgen Symanzik

“Vectors and periodic phenomena, e.g. traffic versus time, have direction on a circular scale of 360°. An overview of existing methods for the display of circular-spatial and vectorial-spatial data, such as arrow plots, is given. We introduce the circular dataimage, a new type of graphic for the display of circular-spatial data. It is defined by encoding direction in a spatial display by using colors from a color wheel constructed by connecting three or more two-color gradients with color continuity at the connections. Therefore, image discontinuity from using a single-color gradient, e.g. blue-red, does not occur. High-resolution global views of ocean wind direction are used as a running example throughout the paper. Advantages and disadvantages of circular dataimages compared to arrow plots were obtained from a usability study. Circular dataimages provide for simultaneous recognition of fine structure on a small-scale and large-scale structure on a global scale.”

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